1. Field of the Invention
This invention relates to the manufacture of a variable insulated wound coil, and more specifically to a new and improved method and apparatus for manufacturing a variable insulated helically wound electrical coil.
2. Description of the Prior Art
In many conventional windings, such as transformer windings, a wire winding for a high voltage section typically uses wire which has an enamel or polymer insulation on it for turn-to-turn insulation and utilizes paper insulation between layers of turns of the coil to provide adequate insulation between the helically wound layers of insulated wire. The layer insulation is generally constructed from sheet material which has a uniform thickness and a width slightly greater than the width of the wire layers. It is wound into the coil as the coil is wound. After each layer of wire has been helically wound onto the coil, one or more turns of the full width layer insulation is wound onto the layer after which the next layer of wire is wound onto the coil. This process repeats through the entire coil. With conventionally wound coils the layer insulation between layers must be thick enough to withstand the highest voltage difference between the layers. Since the windings are continuous and helically wound, the voltage between the layers varies along the coil axis, or width, with the greatest voltage difference between layers occurring between the starting end of a lower layer and the finish end of the layer above it. There is almost no voltage difference between the two layers on the opposite sides of the coil. The thickness of the full width layer insulation must be such that it provides the necessary dielectric strength on the start finish/side where the voltage difference between the layers is the highest. Over the remainder of the layer, the layer insulation is thicker than required. This results in an inefficient use of coil space, and, consequently, greater material usage.
It would be desirable to allow the full width layer insulation to be replaced by insulation that is applied onto the insulated wire so that the wire is insulated only in those areas of the coil where the greatest dielectric strength is needed.